Sucker

Recent abundant flows of Colorado River water between Palisade and the Gunnison River confluence during another spring runoff season weren’t entirely the work of Mother Nature.

They also were the product of a coordinated, voluntary effort by operators of upstream reservoirs to coordinate releases of water into the river to bolster peak flows in that stretch of river and aid in the recovery of endangered fish.

This was the 12th coordinated release since the first one occurred in 1997, and the fifth one in the last six years. The coordinated releases occur as conditions warrant and allow each year, to flush out fine sediment in gravel beds that serve as spawning habitat for rare fish. They also improve habitat for insects and other macroinvertebrates that fish feed on.

The upper Colorado River and its tributaries in Colorado, Utah and Wyoming are home to four endangered fish. Don Anderson, a U.S. Fish and Wildlife Service employee who serves as the instream flow coordinator for the Upper Colorado River Endangered Fish Recovery Program, a public-private partnership, said that what’s known as the 15-Mile Reach of the Colorado River between the Palisade area and the Gunnison River confluence is primarily used by two of the endangered fish, the razorback sucker and Colorado pikeminnow. But a third endangered species, the bonytail, sometimes makes use of the stretch. And a fourth, the humpback chub, which favors deep, rocky, fast-flowing stretches in places such as Westwater Canyon downstream, also indirectly benefits from water releases primarily aimed at bolstering flows in the 15-Mile Reach.

The 15-Mile Reach experiences less of a spring runoff peak than some other parts of the Colorado River because of Grand Valley irrigation diversions just upstream. The goal of this year’s coordinated releases was to achieve daily flows averaging at least 12,900 cubic feet per second upstream at Cameo, an amount that was nearly achieved on some days last week. At times during a couple of days flows exceeded 13,000 cfs, Michelle Garrison, senior water resource specialist for the Colorado Water Conservation Board, told entities involved in the coordinated release program in a conference call Wednesday. She said the effort was a success, and Anderson agreed. He told participants that without getting hung up on exact numbers, flows at that level, which meant peak flows of about 12,000 cfs in the 15-Mile Reach, do good work for the endangered fish and their habitat.

The effort involved in part coordinated releases by the Bureau of Reclamation from Green Mountain Reservoir, Denver Water from Williams Fork Reservoir, and the Colorado River District from Wolford Mountain Reservoir. The Northern Colorado Water Conservancy District also was a participant.

“Man, you guys did a nice job of coordinating as well as you possibly could with the water you had available,” Anderson told reservoir operators.

A dry spring and warm temperatures have hurt forecasts for runoff, including into reservoirs. The coordinated reservoir releases have the goal of not harming water yields or jeopardizing water rights. Reservoirs such as Williams Fork and Green Mountain are still expected to fill this year, although the Bureau of Reclamation had to scale back its Green Mountain releases earlier than planned due to a decrease in forecasted runoff from the Blue River above the reservoir. The Bureau of Reclamation was unable to contribute Ruedi Reservoir water to the effort due to uncertainty about whether it would fill.

Some years, such as 2018, snowpack has been so low that operators worried about even filling their reservoirs weren’t able to undertake a coordinated release that might achieve the 12,900-cfs target. Other years there’s so much snow that officials avoid a coordinated release for fear of causing flood problems.

The coordinated releases can have benefits far beyond the 15-Mile Reach. Anderson said this year’s coordinated releases helped downstream in the Moab area by topping off flows into a wetland that is a potentially valuable razorback sucker nursery. Also, Utah state wildlife officials have reported concerns about seeing smallmouth bass, which prey on endangered fish, possibly spawning for the first time below Westwater Canyon. The coordinated releases may have helped combat that due to the higher and faster flows, cooler water temperatures and increased water turbidity.

Coordinated runoff flows are just one water-delivery effort targeting the 15-Mile Reach. Each year releases of dedicated endangered fish water are made to boost low flows in the reach later in the summer. Also, releases sometimes are made around early April to supplement flows in the reach after irrigation diversions have begun but before the river levels gain from spring runoff. This year was the first year such releases occurred after stored water was specifically held over from last year with the primary goal of possibly serving that purpose.

The Fish and Wildlife Service says various recovery efforts appear to be working, with scientific analysis showing the razorback sucker and humpback chub could be reclassified as threatened under the Endangered Species Act.

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